U.S. patent number 8,220,978 [Application Number 12/801,045] was granted by the patent office on 2012-07-17 for brightness enhancement film and backlight module.
This patent grant is currently assigned to Coretronic Corporation. Invention is credited to Fu-Ming Chuang, Wen-Chih Huang, Ching-Shiang Li, Tzeng-Ke Shiau, Kuo-Tung Tiao.
United States Patent |
8,220,978 |
Shiau , et al. |
July 17, 2012 |
Brightness enhancement film and backlight module
Abstract
A brightness enhancement film (BEF) includes a light
transmissive substrate having a first surface and a second surface,
a plurality of lenses disposed on the first surface, and a
reflective layer. Each of the lenses has a curved protruding
surface facing away from the light transmissive substrate. The
radius of curvature of the curved protruding surface in a first
direction parallel to the first surface is R.sub.1, the radius in a
second direction is R.sub.2, and R.sub.1.noteq.R.sub.2. The
reflective layer is disposed on the second surface and has a
plurality of light pass openings respectively located on the
optical axes of the lenses. The distance between the apex of the
curved protruding surface and the corresponding light pass opening
is L, the refractive index of the lenses is n, and the BEF
satisfies L<nR.sub.1/(n-1) and L<nR.sub.2/(n-1). A backing
light module using the BEF is provided.
Inventors: |
Shiau; Tzeng-Ke (Hsinchu,
TW), Li; Ching-Shiang (Hsinchu, TW), Huang;
Wen-Chih (Hsinchu, TW), Chuang; Fu-Ming (Hsinchu,
TW), Tiao; Kuo-Tung (Hsinchu, TW) |
Assignee: |
Coretronic Corporation
(Hsinchu, TW)
|
Family
ID: |
43300626 |
Appl.
No.: |
12/801,045 |
Filed: |
May 19, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100309682 A1 |
Dec 9, 2010 |
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Foreign Application Priority Data
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Jun 4, 2009 [TW] |
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98118580 A |
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Current U.S.
Class: |
362/607; 313/512;
313/110; 362/620; 362/606; 362/600; 362/610 |
Current CPC
Class: |
G02B
6/0053 (20130101); G02F 1/133606 (20130101); G02B
6/0043 (20130101); G02F 1/133607 (20210101) |
Current International
Class: |
F21V
7/04 (20060101); H01J 1/62 (20060101); H01J
63/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Walford; Natalie
Attorney, Agent or Firm: Bacon & Thomas, PLLC
Claims
What is claimed is:
1. A brightness enhancement film, comprising: a light transmissive
substrate, having a first surface and a second surface opposite to
the first surface; a plurality of lenses, disposed on the first
surface, wherein each of the lenses has a curved protruding surface
facing away from the light transmissive substrate, the radius of
curvature of the curved protruding surface in a first direction
parallel to the first surface is R1, the radius of curvature of the
curved protruding surface in a second direction parallel to the
first surface is R2, and R1.noteq.R2; and a reflective layer
disposed on the second surface, wherein the reflective layer has a
plurality of light transmissive openings, the light transmissive
openings are respectively located on the optical axes of the
lenses, and the distance between the apex of the curved protruding
surface of the lens and the corresponding light transmissive
opening is L, the refractive index of the lenses is n, and the
brightness enhancement film satisfies L<nR1/(n-1) and
L<nR2/(n-1).
2. The brightness enhancement film according to claim 1, wherein
the first direction is substantially perpendicular to the second
direction.
3. The brightness enhancement film according to claim 1, wherein
the widths of the light transmissive openings in the first
direction are not the same as the widths of the light transmissive
openings in the second direction.
4. The brightness enhancement film according to claim 1, wherein
the width of the light transmissive opening in the first direction
is A1, the width of the light transmissive opening in the second
direction is A.sub.2, the width of the curved protruding surface
corresponding to the light transmissive opening in the first
direction is P.sub.1, the width of the curved protruding surface
corresponding to the light transmissive opening in the second
direction is P.sub.2, and the brightness enhancement film satisfies
0.1<A.sub.1/P.sub.1<0.9 and
0.1<A.sub.2/P.sub.2<0.9.
5. The brightness enhancement film according to claim 1, wherein
the widths of at least a part of the lenses are not the same in the
first direction.
6. The brightness enhancement film according to claim 5, wherein
the ratio of the maximum value of the widths of the lenses to the
minimum value of the widths of the lenses in the first direction is
between 1 and 4.
7. The brightness enhancement film according to claim 5, wherein
the widths of at least a part of the lenses are not the same in the
second direction.
8. The brightness enhancement film according to claim 7, wherein
the ratio of the maximum value of the widths of the lenses to the
minimum value of the widths of the lenses in the second direction
is between 1 and 4.
9. The brightness enhancement film according to claim 1, further
comprising a light transmissive layer covering the reflective
surface and being filled in the light transmissive openings.
10. The brightness enhancement film according to claim 1, wherein
the brightness enhancement film satisfies L<0.95nR.sub.1/(n-1)
and L<0.95nR.sub.2/(n-1).
11. A backlight module, comprising: at least one light emitting
device, capable of emitting a light beam; the brightness
enhancement film according to claim 1, disposed in the transmission
path of the light beam; and an optical unit, disposed in the
transmission path of the light beam between the light emitting
device and the brightness enhancement film.
12. The backlight module according to claim 11, wherein the optical
unit comprises a light guide plate, the light guide plate has a
third surface, a fourth surface opposite to the third surface, and
a incident surface connecting the third surface and the fourth
surface, the reflective layer is located between the light
transmissive substrate and the third surface, and the light
emitting device is disposed besides the incident surface.
13. The backlight module according to claim 11, wherein the first
direction is substantially perpendicular to the second
direction.
14. The backlight module according to claim 11, wherein the widths
of the light transmissive openings in the first direction are not
the same as the widths of the light transmissive openings in the
second direction.
15. The backlight module according to claim 11, wherein the width
of the light transmissive opening in the first direction is A1, the
width of the light transmissive opening in the second direction is
A.sub.2, the width of the curved protruding surface corresponding
to the light transmissive opening in the first direction is
P.sub.1, the width of the curved protruding surface corresponding
to the light transmissive opening in the second direction is
P.sub.2, and the brightness enhancement film satisfies
0.1<A.sub.1/P.sub.1<0.9 and
0.1<A.sub.2/P.sub.2<0.9.
16. The backlight module according to claim 11, wherein the widths
of at least a part of the lenses are not the same in the first
direction.
17. The backlight module according to claim 16, wherein the ratio
of the maximum value of the widths of the lenses to the minimum
value of the widths of the lenses in the first direction is between
1 and 4.
18. The backlight module according to claim 16, wherein the widths
of at least a part of the lenses are not the same.
19. The backlight module according to claim 18, wherein the ratio
of the maximum value of the widths of the lenses to the minimum
value of the widths of the lenses in the second direction is
between 1 and 4.
20. The backlight module according to claim 11, wherein the
brightness enhancement film further comprises a light transmissive
layer covering the reflective surface and being filled in the light
transmissive openings, and the light transmissive layer is disposed
between the reflective surface and the optical unit.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application
serial no. 98118580, filed on Jun. 4, 2009. The entirety of the
above-mentioned patent application is hereby incorporated by
reference herein and made a part of this specification.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to an optical film and a light
source module using the optical film, and more particularly, to a
brightness enhancement film (BEF) and a backlight module using the
BEF.
2. Description of Related Art
Along with the development of display technology, flat panel
display has become the main stream of display to take place of
conventional, thick and heavy cathode ray tube (CRT). In flat panel
display, liquid crystal display (LCD) is popular with people, and
widely used. The LCD includes a liquid crystal panel and a
backlight module. The liquid crystal panel may not emit light, and
is used to determine light transmission rate, so a backlight module
is disposed behind the liquid crystal panel and used as a flat
surface light source of the liquid crystal panel. The optical
quality of the flat surface light source greatly affects the
display quality of the LCD. For example, in order to make the
display image to be correctly displayed and have little distortion,
a uniform flat panel light source is needed. Moreover, in order to
improve the brightness of the display image, the range of the light
emitting angle of the flat panel source may also be limited to
avoid the lose of the light.
A conventional side type backlight module has a light guide plate,
besides, a lower diffuser, two prism sheets with prism rods
perpendicular to each other, and a upper diffuser are arranged on
the light guide plate in sequence from down to up, wherein the
prism sheets are used to minimize the range of the light emitting
angle, also the upper diffuser and the lower diffuser are used to
make the light uniform and to avoid producing moire between the
outline of the prism rods and the liquid crystal panel. However,
the method of disposing four optical films on the light guide plate
may increase the cost of the backlight module and too many optical
films may make assembly difficult and be difficult to reduce the
thickness of the backlight module.
In addition, the Taiwan patent publication number 200911513
discloses an optical film structure disposed on the light guide
plate. The optical film structure has a light transmissive body and
a reflective layer disposed on the light incident surface of the
light transmissive body, and a lens array is disposed on the light
emitting surface of the light transmissive body. Moreover, an
opening corresponding to the lens is disposed at the reflective
layer. In addition, the American publication number 20070002452
also discloses the same type optical film structure. However, to
the different demands of brightness distribution at different
angles in different directions, the backlight modules of the liquid
crystal display of different electronic equipments (such as mobile
phone, notebook computer, monitor TV and other liquid crystal
display) using the optical film structures of the two above
mentioned patent have difficulty to make the range of the light
emitting angle change with the changing of the direction, so the
design concepts of the mentioned patents above are difficult to
apply to different kinds of electronic equipments at the same
time.
SUMMARY OF THE INVENTION
The invention provides a brightness enhancement film (BEF) capable
of making the light beam through the BEF have different light
emitting angles in two different directions, and be manufactured
easily.
The invention provides a backlight module having low cost and good
optical character, easy to be assembled, and apply to different
kinds of electronic equipments.
Other advantages of the invention may be further indicated by the
disclosures of the invention.
To achieve at least one of the objectives, one embodiment of the
invention provides a light enhancement film (BEF) including a light
transmissive substrate, a plurality of lenses, and a reflective
layer. The light transmissive substrate has a first surface and a
second surface opposite to the first surface. The lenses are
disposed on the first surface, wherein each of the lenses has a
curved protruding surface facing away from the light transmissive
substrate. The radius of the curved protruding surface in a first
direction parallel to the first surface is R1, the radius of the
curved protruding surface in a second direction parallel to the
first surface is R2, and R.sub.1.noteq.R.sub.2. The reflective
layer is disposed on the second surface, wherein the reflective
layer has a plurality of light transmissive openings, and the light
transmissive openings are respectively located on the optical axes
of the lenses. The distance between the apex of the curved
protruding surface of the lens and the corresponding light
transmissive opening is L, the refractive index of the lenses is n,
and the BEF satisfies L<nR.sub.1/(n-1) and
L<nR.sub.2/(n-1).
In one embodiment of the invention, the first direction is
substantially perpendicular to the second direction. The widths of
the light transmissive openings in the first direction are not the
same as the widths of the light transmissive openings in the second
direction. The width of the light transmissive opening in the first
direction is A.sub.1, the width of the light transmissive opening
in the second direction is A.sub.2, the width of the curved
protruding surface corresponding to the light transmissive opening
in the first direction is P.sub.1, the width of the curved
protruding surface corresponding to the light transmissive opening
in the second direction is P.sub.2, and the BEF satisfies
0.1<A.sub.1/P.sub.1<0.9 and
0.1<A.sub.2/P.sub.2<0.9.
In one embodiment of the invention, the widths of at least a part
of the lenses are not the same in the first direction. The ratio of
the maximum value of the widths of the lenses to the minimum value
of the widths of the lenses in the first direction is, for example
between 1 and 4. The widths of at least a part of the lenses are
not the same in the second direction. The ratio of the maximum
value of the widths of the lenses to the second direction is, for
example, between 1 and 4. The BEF may further include a light
transmissive layer covering the reflective layer and being filled
in the light transmissive openings. The BEF satisfies
L<0.95nR.sub.1/(n-1) and L<0.95nR.sub.2/(n-1).
Another embodiment of the invention provides a backlight module
including at least a light emitting device, above mentioned BEF and
an optical unit. The light emitting device is capable of emitting a
light beam. The BEF is disposed in the transmission path of the
light beam. The optical unit is disposed in the transmission path
of the light beam between light emitting device and the BEF.
In one embodiment of the invention, the optical unit includes a
light guide plate having a third surface, a fourth surface opposite
to the third surface and a light incident surface connecting the
third surface and the fourth surface. The reflective layer may be
located between the light transmissive substrate and the third
surface, and the light emitting device may be disposed besides the
light incident surface. The light transmissive layer may be
disposed between the reflective layer and the optical unit.
In the BEF of the embodiment of the invention, for
R.sub.1.noteq.R.sub.2, the BEF may be used in the backlight module
having different demands at the ranges of light emitting angle in
different directions. By appropriately designing the values of
R.sub.1 and R.sub.2, the backlight module using the BEF may be used
in different kinds of display. Moreover, in the embodiment of the
invention, the BEF satisfies L<nR.sub.1/(n-1) and
L<nR.sub.2/(n-1), so in manufacturing process, when the parallel
laser beam perpendicular to the first surface transmits to the lens
by the technique of laser drilling and the laser beam is
concentrated to the reflective layer by lens and produces a light
spot, the illumination distribution of the light spot may be more
uniform. In that way, just once drilling action using parallel
laser beam, the light transmissive openings having prospective
dimension and position may be drilled out, so the BEF of the
embodiment of the invention may simplify the manufacturing process,
so that the cost of the embodiment of the backlight module may be
reduced. Moreover, when the BEF satisfies L<nRi/(n-1) and
L<nR.sub.2/(n-1), the light beam through the BEF may become more
ur form, then the backlight module of the embodiment of the
invention may provide more uniform surface light.
Other objectives, features and advantages of the invention will be
further understood from the further technological features
disclosed by the embodiments of the invention wherein there are
shown and described preferred embodiments of this invention, simply
by way of illustration of modes best suited to carry out the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention.
FIG. 1A and FIG. 1B are cross-sectional diagrams of a backlight
module of an embodiment of the invention in two different
directions perpendicular to each other.
FIG. 2A is a stereogram of the brightness enhancement film (BEF) in
FIG. 1A.
FIG. 2B is a bottom view diagram of the BEF in FIG. 1A.
FIG. 3A is a diagram showing the illumination distribution of light
spot in laser drilling process of the BEF in FIG. 1A.
FIG. 3B is another illumination distribution of the light spot in a
condition different from FIG. 3A.
FIG. 4A is a bottom view diagram of the BEF according to another
embodiment of the invention.
FIG. 4B is a bottom view diagram of the BEF according to another
embodiment of the invention.
FIG. 5 is a cross-sectional diagram of the backlight module
according to another embodiment of the invention.
DESCRIPTION OF THE EMBODIMENTS
In the following detailed description of the preferred embodiments,
reference is made to the accompanying drawings which form a part
hereof, and in which are shown by way of illustration specific
embodiments in which the invention may be practiced. In this
regard, directional terminology, such as "top," "bottom," "front,"
"back," etc., is used with reference to the orientation of the
Figure(s) being described. The components of the invention can be
positioned in a number of different orientations. As such, the
directional terminology is used for purposes of illustration and is
in no way limiting. On the other hand, the drawings are only
schematic and the sizes of components may be exaggerated for
clarity. It is to be understood that other embodiments may be
utilized and structural changes may be made without departing from
the scope of the invention. Also, it is to be understood that the
phraseology and terminology used herein are for the purpose of
description and should not be regarded as limiting. The use of
"including," "comprising," or "having" and variations thereof
herein is meant to encompass the items listed thereafter and
equivalents thereof as well as additional items. Unless limited
otherwise, the terms "connected," "coupled," and "mounted" and
variations thereof herein are used broadly and encompass direct and
indirect connections, couplings, and mountings. Similarly, the
terms "facing," "faces" and variations thereof herein are used
broadly and encompass direct and indirect facing, and "adjacent to"
and variations thereof herein are used broadly and encompass
directly and indirectly "adjacent to". Therefore, the description
of "A" component facing "B" component herein may contain the
situations that "A" component directly faces "B" component or one
or more additional components are between "A" component and "B"
component. Also, the description of "A" component "adjacent to" "B"
component herein may contain the situations that "A" component is
directly "adjacent to" "B" component or one or more additional
components are between "A" component and "B" component.
Accordingly, the drawings and descriptions will be regarded as
illustrative in nature and not as restrictive.
Referring to FIG. 1A, FIG. 1B, FIGS. 2A and 2B, the backlight
module 100 of the embodiment includes a light emitting device 110,
a beam enhancement film (BEF) 200, and an optical unit 300. The
light emitting device 110 is capable of emitting a light beam 112.
In the embodiment, the light emitting device 110 is, for example, a
cold cathode fluorescent lamp (CCFL). However, in other embodiment,
the backlight module may have a plurality of light emitting
devices, for example, light emitting diodes (LEDs) arranged in a
straight line.
The BEF 200 is disposed in the transmission path of the light beam
112. The optical unit 300 is disposed in the transmission path of
the light beam 112 between the light emitting device 110 and the
BEF 200. In the embodiment, the optical unit 300 includes a light
guide plate 310 having a surface 312, a surface 314 opposite to the
surface 312, and a light incident surface 316 connecting the
surface 312 and the surface 314. The light emitting device 110 may
be disposed besides the light incident surface 316. Specifically,
the light beam 112 emitted from the light emitting device 110 may
transmit to the light guide plate 310 through the light incident
surface 316, and the light beam 112 may be confined in the light
guide plate 310 through being totally internally reflected by the
surface 312 and the surface 314. However, the microstructure 315 on
the surface 314 of the light guide plate 310 may destroy the total
internal reflection. For example, a part of the light beam 112 may
be reflected to surface 312 by the microstructure 315 and transmit
through the surface 312. The other part of the light beam 112 may
penetrate the microstructure 315 and transmit to a reflective plate
320 disposed at one side of the surface 314. The light beam 112 may
be reflected by the reflective plate 320 and penetrate the surface
314 and the surface 312 in sequence.
The BEF 200 includes a light transmissive substrate 210, a
plurality of lenses 220, and a reflective layer 230. The
transmissive layer 210 has a second surface 214 and a first surface
212 opposite to each other. The lenses 220 are disposed on the
first surface 212, wherein each of the lenses 220 has a curved
protruding surface 222 facing away from the light transmissive
substrate 210. The radius of the curvature of the curved protruding
surface 222 in a first direction D1 parallel to the first surface
212 is R.sub.1, the radius of the curvature of the curved
protruding surface 222 in a second direction D2 parallel to the
first surface 212 is R.sub.2, and R.sub.1.noteq.R.sub.2. In the
embodiment, the curved protruding surface 222 may be smooth curved
surface, or the curved protruding surface 222 may consist of a
plurality of tiny straight line segment or curved line segment.
Besides, the first direction D1 is substantially perpendicular to
the second direction D2. The reflective layer 230 is disposed on
the second surface 214, wherein the reflective layer 230 has a
plurality of light transmissive openings 232, and the light
transmissive openings 232 are disposed on the axis X of the lenses
220. In the embodiment, the reflective layer 230 may be disposed
between the light transmissive substrate 210 and the surface 312.
The distance between the apex T of the curved protruding surface
222 of the lenses 220 and the corresponding light transmissive
opening 232 is L, and the refractive index of the lenses 220 is n,
and the BEF 200 satisfies L<nR.sub.1/(n-1) and
L<nR.sub.2/(n-1).
When the light emitting angle of the light beam 112 emitting from
the surface 312 is too big, most part of the light beam 112 may be
reflected to the light guide plate 310 by the reflective layer 230
and be used again. When the light emitting angle of the light beam
112 departing from the surface 312 is small, more proportion of
light beam 112 may be through the light transmissive openings 232.
The light energy distribution of the light beam 112 through the
light transmissive openings 232 is, for example, approximate Gauss
distribution, and the light beam 112 may be concentrated by the
lenses 220 and be emitted out from the lenses 220 in an angle
approximately perpendicular to the first surface 212. Thus the
backlight module 100 of the embodiment may reduce the range of the
light emitting angle by one single optical film (the BEF 200), then
the illumination of the liquid display is improved, and the
backlight module 100 may not adopt four optical films as used in
prior art.
Besides, in the BEF 200 of the embodiment, for
R.sub.1.noteq.R.sub.2, the BEF may be used in the backlight module
having different demands at the ranges of the light emitting angle
in different directions. Through appropriate designing of the
values of R.sub.1 and R.sub.2, the backlight module adopting the
BEF 200 may be used in different kinds of display of the electronic
equipment, such as mobile phone, notebook, monitor, TV and other
equipments using liquid crystal display.
In the embodiment, the widths of the light transmissive openings
232 in the first direction D1 are not the same as the widths of the
light transmissive openings 232 in the second direction D2.
Besides, the width of the light transmissive opening 232 in the
first direction D1 is A.sub.1, the width of the light transmissive
opening 232 in the second direction is A.sub.2, the width of the
curved protruding surface 222 corresponding to the light
transmissive opening 232 in the first direction D1 is P.sub.1, the
width of the protruding surface 222 corresponding to the light
transmissive opening 232 in the second direction D2 is P.sub.2, and
the BEF 200 may satisfies 0.1<A.sub.1/P.sub.1<0.9 and
0.1<A.sub.2/P.sub.2<0.9. Thus the range of the light emitting
angle in the first direction D1 and the range of the light emitting
angle in the second direction D2 may have great variation, so that
the BEF 200 and the backlight module 100 may be used more
widely.
In the embodiment, the light transmissive opening 232 of the
reflective layer 230 may be made by laser drilling technique.
Specifically, before the laser drilling process, the reflective
layer 230 is entirely distributed on the second surface 214. Later,
the laser beams parallel to each other emit to lens 220 from the
right upside of the BEF 200 in FIG. 1A, that is, the laser beams
emit to lens 220 along the direction perpendicular to the first
direction D1 and the second direction D2. As a result of the
concentration of the lens 220, the light spot formed on the
reflective layer 230 by the laser beam is at the position of the
light transmissive opening 232, and the illumination distribution
of the light spot is described as FIG. 3A. As shown in FIG. 3A,
because the illumination distribution of the light spot is uniform,
so long as the power of the laser beam is big enough, the light
transmissive opening 232 as big as the light spot may be drilled
out at the reflective layer 230, and the illumination distribution
of the light spot is formed on condition of the BEF 200 satisfying
L<nR.sub.1/(n-1) and L<nR.sub.2/(n-1). Thus only once
drilling action using the parallel laser beam, the light
transmissive openings 232 having prospective size and position may
be drilled out, so the design of the BEF 200 of the embodiment may
simplify the manufacture process and reduce the cost of the
backlight module 100. Contrarily, if the BEF 200 satisfies
L>nRi/(n-1) and L>nR.sub.2/(n-1), the illumination
distribution of the light spot is distributed as FIG. 3B. As shown
in FIG. 3B, the illumination of the light spot in the center is
higher than the illumination of the light spot around the center,
the distribution of the energy has no obvious boundary, and the
size of the light transmissive opening 232 is hard to control, so
that the size of the light transmissive opening 232 is smaller than
the size of the light spot, and the size of the light transmissive
232 may not satisfy the prospective size. As a result, the incident
angle of the laser beam may be modified to drill several times to
make the size and the position of the light transmissive opening
232 satisfy the prospective size and position. So the manufacture
process may be too complicated, and the manufacture cost and
manufacture time may be increased.
Moreover, the condition of making the BEF 200 satisfy
L<nRi/(n-1) and L<nR.sub.2/(n-1) may also make the light beam
112 transmitted through the BEF 200 more uniform. In the
embodiment, the BEF 200 satisfies L<0.95nRi/(n-1) and
L<0.95nR.sub.2/(n-1) to further improve the uniformity of the
light beam 112 transmitted through the BEF 200.
In order to make the BEF 200 have better light efficiency, the BEF
200 may further include a light transmissive layer 240 covering the
reflective layer 230 and being filled in the light transmissive
openings 232. The process forming the light transmissive layer 240
may be after the laser drilling process. In the embodiment, the
light transmissive layer 240 is disposed between the reflective
layer 230 and the optical unit 300. The light transmissive layer
240 may make the light beam 112 be refracted (for example refracted
by the interface between the air and the light transmissive layer
240) before transmitting into the light transmissive layer 232 to
minimize the incident angle, so that the situation of the light
beam 112 emitting to another lens 220 besides the lens 220
corresponding to the light transmissive opening 232 may be reduced
and the efficiency of the BEF 200 may be improved. Thus the
backlight module 100 may have higher light efficiency. In the
embodiment, the refractive index of the light transmissive layer
240 is, for example, in the range of from 1.45 to 1.6, the
refractive index of the light guide plate 310 is, for example, 1.5,
the refractive index of the air is, for example, 1, and the
refractive index of the light transmissive substrate and the
refractive index of the lens 220 may be the same. However, in other
embodiment, the BEF 200 may not have the above mentioned light
transmissive layer 240.
Referring to FIG. 4A, the BEF 200' of the embodiment is similar to
the BEF 200 in FIG. 2B, and the differences are described as below.
In the BEF 200' of the embodiment, the widths P.sub.1 of at least a
part of the lenses 220 are not the same in the first direction D1.
The ratio of the maximum value of the widths P.sub.1 of the lenses
220 to the minimum value of the widths P.sub.1 of the lenses 220 in
the first direction D1 is between 1 and 4. Besides, in the
embodiment, the widths P.sub.2 of at least a part of the lenses 220
are not the same in the second direction D2. The ratio of the
maximum value of the widths P.sub.2 of the lenses 220 to the
minimum value of the widths P.sub.2 of the lenses 220 in the second
direction D2 is between 1 and 4. Designing the size and the
position of the lens 220 irregularly may reduce the moire
phenomenon between the BEF 200' and the liquid crystal panel (not
shown) disposed on the BEF 200'.
Referring to 4A and 4B, the differences of the BEF 200'' (as
described in FIG. 4B) of the embodiment and the BEF 200' (as
described in FIG. 4A) are shown as below. The widths P.sub.2 of the
lenses 220 in the same line of the BEF 200' are substantially the
same in a direction (for example, the first direction D1), and the
widths P.sub.1 of the lenses 220 in the same line of the BEF 200'
are at least partially the same in another direction (for example,
the second direction D2). However, in the first direction D1 or in
the second direction D2, the widths P.sub.1 or the widths P.sub.2
of the lenses 220 in the same line of the BEF 200'' are both at
least partially not the same. The BEF 200'' has higher
irregularity, and thus the BEF 200' may be manufactured and
designed easily.
Referring to FIG. 5, the backlight module 100a of the embodiment
and the backlight module 100 are partially similar, and the
differences between the backlight module 100a and the backlight
module 100 are described as below. The backlight module 100 is side
type backlight module, and the backlight module 100a is direct type
backlight module. Specifically, the optical unit 300a includes a
light diffusion plate 330, wherein the light diffusion plate 330 is
disposed between the BEF 200 and a plurality of light emitting
devices 110. That is one of the characters of the direct type
backlight module. The light beams 112 emitted from the light
emitting device 110s may transmit into the BEF 200 through the
light diffusion plate 330 and be diffused by the diffusion plate
330. In the embodiment, the backlight module 100a further includes
a lamp case 340, and a plurality of light emitting devices 110 are
disposed in the lamp case 340. The inner wall of the lamp case 340
has reflective function and may reflect the light beams 112 from
the light emitting devices 110 to the light diffusion plate
330.
In conclusion, the embodiment or the embodiments of the invention
may have at least one of the following advantages, in the BEF of
the embodiment of the invention, for R.sub.1.noteq.R.sub.2, the BEF
may be used in the backlight module having different demands at the
ranges of the light emitting angle in different directions. By
appropriately designing the values of R.sub.1 and R.sub.2, the
backlight module adopting the BEF may be applied to the display of
all kinds of different equipments. Besides, the BEF of the
embodiment of the invention satisfies L<nR.sub.1/(n-1) and
L<nR.sub.2/(n-1), so in manufacturing process, when the parallel
beams perpendicular to the first surface emit to lens by laser
drilling technique, and the laser beams are concentrated to the
reflective layer by the lenses and produce light spots, the
illumination distribution of the light spots may be more uniform.
Thus only once drilling action using the laser beam, the light
transmissive openings having perspective size and position may be
drilled out, so the BEF of the embodiment of the invention may
simplify the manufacture process and further reduce the cost of the
backlight module of the embodiment of the invention. Moreover, the
condition of making the BEF satisfy L<nRi/(n-1) and
L<nR.sub.2/(n-1) may also make the light beam through the BEF
more uniform, and make the backlight module of the embodiment of
the invention provide more uniform surface light.
The foregoing description of the preferred embodiments of the
invention has been ed for purposes of illustration and description.
It is not intended to be exhaustive or to limit the invention to
the precise form or to exemplary embodiments disclosed.
Accordingly, the foregoing description should be regarded as
illustrative rather than restrictive. Obviously, many modifications
and variations will be apparent to practitioners skilled in this
art. The embodiments are chosen and described in order to best
explain the principles of the invention and its best mode practical
application, thereby to enable persons skilled in the art to
understand the invention for various embodiments and with various
modifications as are suited to the particular use or implementation
contemplated. It is intended that the scope of the invention be
defined by the claims appended hereto and their equivalents in
which all terms are meant in their broadest reasonable sense unless
otherwise indicated. Therefore, the term "the invention", "the
invention" or the like does not necessarily limit the claim scope
to a specific embodiment, and the reference to particularly
preferred exemplary embodiments of the invention does not imply a
limitation on the invention, and no such limitation is to be
inferred. The invention is limited only by the spirit and scope of
the appended claims. The abstract of the disclosure is provided to
comply with the rules requiring an abstract, which will allow a
searcher to quickly ascertain the subject matter of the technical
disclosure of any patent issued from this disclosure. It is
submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims. Any
advantages and benefits described may not apply to all embodiments
of the invention. It should be appreciated that variations may be
made in the embodiments described by persons skilled in the art
without departing from the scope of the invention as defined by the
following claims. Moreover, no element and component in the
disclosure is intended to be dedicated to the public regardless of
whether the element or component is explicitly recited in the
following claims.
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